The present invention relates to a stacking arrangement for planks and boards, particularly profile strips, with at least two stacking units and a stacking element holding the lumber. The stacking arrangements and stacking element can be moved relative to one another; each of the stacking elements has a movable support arm and a transport device for the lumber to be deposited on the support arm.
With a known stacking arrangement of the preceding species, the transport device comprises a slide actuated by a lift magnet. The slide moves the lumber to be stacked onto the extended support arm. After filling a stacked row, before pulling back the support arm, a retainer is moved vertically by means of another lift magnet; this retainer secures the lumber stacked row against a return movement together with the returning (retracting) support arm. This known stacking arrangement, furthermore, requires a relatively cumbersome control device because slide and retainer are separate components whose consequent co-ordination requires additional control elements. If the stacked rows that are stacked on the stacking element, e.g., an ordinary pallet are separated from one another by intermediate sticker layers which are placed on the support arms by hand or by means of a suitable magazine, there is danger that during retraction of the support arms the intermediate layers are also pulled back, since the retainer only grasps the lumber (to be) stacked.
When using the known stacking arrangement, there have been additional difficulties at the instant of retraction of the support arm with simultaneous deposition of the intermediate layers with the profile strips. Due to a certain distance between the surface of the stacked row deposited last and a certain thickness of the support arm, the row to be deposited now must be lowered by the sum of these two amounts during retraction of the support arms. After a partial retraction of the support arm, there results a tilting of the intermediate layer with the profile strips around the leading edge of the support arm. At this instant there is danger that profile strips, particularly those with smooth surfaces are displaced on the intermediate layers and possibly might even slide off. Particularly when stacking the profile strips with interstices there is the danger that the interstices formed during deposition of the profile strips on the intermediate layers resting on the support arms may be changed or may be closed up altogether.
There also have been difficulties during insertion of the intermediate layers in the magazines. In particular, there have been problems with the insertion of the intermediate layers into the groove of the support arm when the cross-section of the intermediate layers was not square but rectangular.
It is, therefore, an object of the present invention to provide a stacking arrangement of the initially mentioned type which as a transporting device requires only a simple control device which gives absolute certainty that during retraction of the support arms, the intermediate layers are not retracted also, and which further makes sure that during deposition of a stacked row on the support arms onto the stacked row already deposited, there is no shifting of the profile strips on the intermediate layers. The insertion of the intermediate layers into the magazines and into the groove of the support arm is also to be simplified.
Another object of the present invention is to provide a stacking arrangement of the foregoing character which may be economically fabricated and readily maintained in service.
A still further object of the present invention is to provide a stacking arrangement, as described, which has a substantially long operating life.